My latest project

[zombiepotatosalad]

Here is my '77 R100S, needs a bit of work. Maybe a bit more than I thought.

I'll have to clean and rebuild the carbs.
It feels like only a couple gears are engaging from a simple roll test, it feels like I can only get 3 shifts up or down.
The ignition cylinder appears stuck, I'll have to put some PB Blaster in it.
The front steering feels really stiff, like it's obstructed by an object when I try to turn.
The seat is from an RT, but this bike is an S. Anyone want to trade seats?

20221118_111438.jpg20221118_111444.jpg20221118_111451.jpg20221118_111936.jpg

[20774]

Welcome! Quite the project...bummer that you have to work outside. You say it is an R100S but everything about the bike appears to be an RT. What clues do you see that says R100S? If you got to RealOEM and type in the VIN located next to the oil fill hole, you should see on the screen the type of bike and month/year of build. You can also go to this website and go to the 1000cc page to find your serial number:

http://www.bmbikes.co.uk/enginechassis.htm

[zombiepotatosalad]

Welcome! Quite the project...bummer that you have to work outside. You say it is an R100S but everything about the bike appears to be an RT. What clues do you see that says R100S? If you got to RealOEM and type in the VIN located next to the oil fill hole, you should see on the screen the type of bike and month/year of build. You can also go to this website and go to the 1000cc page to find your serial number:

http://www.bmbikes.co.uk/enginechassis.htm

"Everything?" What do you mean, everything? You know, I thought the front fairing looked different than the standard. Like those side compartments, the airflow nozzles.
As for evidence, the "VIN" listed on the title says "R100S6160173." RealOEM sorts this further: It's an R100S, made in August of 1976 (I thought September was the start of the new model year). The top cover of the engine also says R100S. For sake of argument, where is the oil fill hole? 16688117994672171672563488417698.jpg

[20774]

Well, looks like you've been down that road. Right on the VIN and I didn't see the engine badge in the pictures. I guess what I see is the fairing with is an RT so apparently somewhere in the past, it got the fairing, etal, to make it look like an RT. I notice you've got the cool oil temp gage filler cap! The wheels are probably Lesters, not original BMW wheels.

I, too, heard that the model years usually begin in September...my '78 R100/7 was built in August 1977. But the first year /7 models got a jump on things and you will see '77 models built as early as the summer, especially R100RS models.

[zombiepotatosalad]

That's really interesting! If only I could view the history as one can with a proper VIN. It would appear this was a stylistic choice rather than a "repairing damage" one. I don't see any warps in the frame, and the only scuff marks are on the cylinder heads, which seem to be common with this type of engine.

[STEVENRANKIN]

It is surprisingly easy to covert an S to a RT, well, lol mostly easy, The RT fairing bracket bolts on to the front of the steering head it is not a terribly difficult job to drill the two holes and tap them if they weren't there already. My old dealer had a RT fairing from a first year 79 RT on his 74 R90S very pretty in the silver smoke. The RT was out either the later part of 78 or 79. St.

[melville]

S bikes had the cowled seat just like RT or RS bikes, so if you can source an R100S badge for the seat that's all you need to change it up.

German factories, and most European factories, would have the model change happen in August while most of their workers were on vacation. August is the classic summer vacation month all over Europe.

[STEVENRANKIN]

The serial number will tell the story as to what the bike was at its birth. I will ask, does the engine serial number match the frame on this bike? It would not be the first time engines have been swapped out from one model to another. St.

[Pauls1150]

Since nobody has answered his question - the "oil fill hole" is immediately under that temperature gauge with the big hex, on the left side of the engine behind the cylinder. Hopefully the gauge has the correct length of dipstick (for checking the oil level) attached to it.
(That black rubber piece to the rear of it is for viewing the timing marks.)

I thought that BMW quit "matching" frame and engine numbers with earlier airheads...?

Also, it sounds like new (or at least, "serviced") neck bearings should be on the to-do list.

[20774]

I thought that BMW quit "matching" frame and engine numbers with earlier airheads...?

As far as I know, they began matching engine and frames around the beginning of WWII. Per Snowbum, BMW began to phase out the use of VINs on the engine with the 1984 model, so well into the Airheads. There are likely some '84s with stamping around the oil fill hole, but it stopped at some point. It was documented in a Service Bulletin in late 1983.

[Pauls1150]

Thanks, Kurt! I really can't recall, but I think there was some stamping there on both of my /5's... but it was much shorter than the full VIN, maybe just the last few digits... dunno.

[m_stock10506]

According to the Snowbum article:

"The 17 character VIN system was introduced in 1980-1981."

"The engine and frame number prior to 1980 was 7 digits."

[STEVENRANKIN]

My 84 has no serial number stamped on the engine, my late 78 did, this bike in question should have both numbers.

The ATE brakes point to this being a 77 to 80 model year bike, 81 started the Brembo brakes.

in this case, the owner has a choice, keep it in RT trim or if the bike is indeed an S model, remove the fairing and brackets, lights handlebars cables and install an S fairing with all the work involved. It depends on what he wants to do, personally I would leave it as an RT, clean it up tune it up and ride it.

For the 79 to 80 engines I believe a lot of parts are the same for the S and the RT, but it would be nice to know exactly what year and model engine is in the frame. St.

[zombiepotatosalad]

My 84 has no serial number stamped on the engine, my late 78 did, this bike in question should have both numbers.

The ATE brakes point to this being a 77 to 80 model year bike, 81 started the Brembo brakes.

in this case, the owner has a choice, keep it in RT trim or if the bike is indeed an S model, remove the fairing and brackets, lights handlebars cables and install an S fairing with all the work involved. It depends on what he wants to do, personally I would leave it as an RT, clean it up tune it up and ride it.

For the 79 to 80 engines I believe a lot of parts are the same for the S and the RT, but it would be nice to know exactly what year and model engine is in the frame. St.

Here you go, a matching set!
20221119_162812.jpg20221119_162818.jpg20221119_162839.jpg

[Omega Man]

Nice!
Welcome to the forum!
Sometimes you can make a makeshift “garage” with some tarps and supply some light and heat with 500 watt quartz light.
Good luck.
Gary